Thread-tension mechanism for sewing machines



Feb, 10. 1 925.. v A. F; FIFIELD THREAD TENSI'ON MECHANISM FQR SEWING mcniuzs File d Dec. 2. 1922 SheetS-Shqet 1 WITNESS ES 2 .uu wa ATTORNEY Feb, 10. 1925.-

I A. F. FIFIELD THREAD TENSION MECHANISM FOR SEWING MACHINES 2 sheets-sheet 2 Filed Dec. 2. i922 INVENTOR #65 Z ATTORNEY Patented Feb. 10, 1925.

run M PATENT "QFFEICTE.

ALBERT FIFIELD, 0E NEWARK, NEW JERSEY, ASSIGN-OR TO :THE *SINGER'MANU- FAGTURlN'G- COMIPAINY,OF ELIZABETH, NEVJ NERSEY, CORIE'ORATION 10F -NEW JERSEY.

THREAD IENSION'MEGHANISMsFGR STARTING MACHINES.

Application filed December 2, 1922. .ScriaLNo. 604,469.

To, all whom it may concern:

Be it known that I, ALnnRrF. Ftrmno, a citizen of the United States, residing at Newark, in the county of Essex and State of New Jersey, have invented. certain new and useful Improvements in Thread-Tension Mechanisms for Sewing Machines, of which the .iiollowing is i a specification, reference being had therein to the accompanying drawings.

This invention relates to sewing machines and" particularly to sewing machines of the typesadapted to form a group or predetermined number of stitches and then come to rest. Suchunachines are adapted ton tacking, barring, sewing on buttons etc, andare customarily equipped with a stop-motion.

device for arresting theoperation oi the machine latter the desired group of stitches has been formed. Such machines are also customarily 1 equipped with thread-cutting andthread-end holding mechanism for sevcring. the sewing thread at the completion of each sewing operationand for holding the beginning end of the needle-thread during the formation of the initial stitches :ot a group.

Heretofore, more or less :diiiiculty has been experienced, particularly with rotary- .looper chain-stitch machines havingan intermittent. thread-tension, in sewing the initial stitches ;.the thread being either broken or pulled out of the threadend holding device. "Some machines employ a pull-off for su 'iplying slack thread to enable the initial stitches to beformed but it is ditiicult to produce satisfactory work on such machines for. the reason thatwwhere a pull-oft is used there is a pronounced tendency for the initial stitchesto be loosely set up.

in the machine disclosed in niycopending application Serial No. 435,599, filed January 7, 1921,.thereis employed a threadgripper below the throat-plate and an intermittent tension or thread-lock at: the. rear end of the bracket-arm; a yielding thread' guide being provided adjacent the upper end of theneedle-bar to yield enoughslack thread to prevent the beginning end of the thread ironibeing pulled out of the grip )er onthe second up-sstroke of the needle-bar. In this machine, however, the tension of the yielding thread guide is. made heavy so that said guidewill not; yield to normal sewing Hilllliiiiliiiwithin...

strains onthe thread but will function :as

a stationary thread guide except when the thread is subjected to abnormal strain, as when sewing the initial stitches,..at which latter time the threadis subjected tothe rather heavy tension imposed by the yielding. thread-guide as ityields enough to' balance the rather heavy tension of the threadgripper below. the throat-plate. While such a machine is satisfactory for sewing on buttons it is found that it is not well adapted for sewing work of a yielding or easily damaged character, suchtas the sewing of paper tickets on clothing, inasmuchas the heavyinitial tension. on thethread causes the thread between the first and second needlepunctu-res to cut through the paper.

An object of the invention, therefore, is to'improve the thread-controllingunechanism disclosed in my said copending application, so that. the machine will sew soft or easily damaged work in-a satisfactory manner.

Another object of, the invention is to, provide a sewing machine of the class described, with means whereby the beginning threadend. may be controlled and the initial stitches properly formed and set up, without subjecting the thread to: heavy tension.

Another object of the invention is to obviate the necessity of providing the machine with a pull-off for. supplying slack thread for the sewing of. the initial stitches, as. has heretofore been done to prevent. the beginning thread end from being pulled out of the gripper, as the use of a pull-oti usually results in loosely set up initial stitches.

Further objects of the invention will in part be obvious and in part more fully hereinafter described.

To the ends i11.view,- thc tension device and, in rotary-.looper chain-stitch machines, the intermittent tension device orthreadlock, is provided with'an automatic or feedcai'n operated connection whereby the thread will be permitted to run. under a lightv tens sion from the supply as the looper is draw- 7 transverse section through the overhanging bracket-arm of the machine, looking toward the standard. Fig. 3 is a fragmentary top plan view of the machine. Fig. l is a bot-- tom plan view of the throat-plate of the machine. Fig. is a vertical s ction through the tension device. Fig. 6 is a large scale elevation of the yielding thread guide adjacent the needle-bar. Fig. 7 is a fragmentary front end elevation of the brackeharn'i. Fig. 3 is a section on the line 8, 8, Fig 1.. Fig. 9 is a section on the line 9, 9, Fig 1. Fig. 10 is an elevation of the adjusting screw for timing the tension releasing mech anism. Fig. 11 a plan view of the lower work clamping member or work supporting plate. Fig. 12 is a plan view of the upper clamping member or foot and Fig. 13 illustrates a sample of work produced by the particular machine chosen for the purposes of the present disclosure.

For the purposes of the present disclosure, the invention will be described as ea:- bodied. in a Singer class lll single-thread sewing machine such as disclosed in my said copending application. Such a machine comprises a base 1, work-supporting arm 2,

standard 3 and overhanging bracket-arm 4-.

terminating in the head in which are our-- naled the usual clamp-opening and needle-- bars 6 and 7, respectively, the latter carrying the needle 8 which cooperates with the rotary looper 9 to form single-thread chain-stitches.

The mechanism of the machine is operated by the usual connections with the inain-shaft which is journaled within and longitudinally of the bracket-ari'n 4: and at its rearward end carries the tight and loose pulleys l1, 12, for the driving belt which runs through the beltshifting guide 13 carried by the starting and stopping lever ll of the usual automatic stopanotion device such as shown in the patent to J. J. Sullivan, No. 777,56a, of December 13, 1904;. This stop-mechanism automatically brings the machine to rest with the needle out of the work at the end of each stitching period, or after a predetermined number of stitches have been formed.

As is usual in machines this character. mechanism is provided for producing relalive movement between the work and needle to group the stitches according to the desired arrangement. This mechanism which is substantially that disclosed in the Sul- .livan patent above referred to, comprises a feedwheel 15 mounted in a vertical plane at one side of the standard 3 on a shaft 16 passing transversely through the stand ard 3 and carrying a gear 17 with which meshes a driving worm 18 on the main-shaft 10. The feed-wheel is formed in its side faces with lateral and longitudinal feed cam-grooves l9 and .20. respectively, en-

tered by follower rolls 21, 22, carried respec tively by the usual lateral and longitudinal feed connections with the work-clamp 23 carried by the clamp supporting bar slidably mounted on the bed 2. The workclamp includes a lower work-supporting plate 24 and an upper clamping foot 25 between which the Work is held for the stitching operation. The present machine is adapted to attach paper tickets (6 to clothing 6 by a triangular tack or group of single thread chain-stitches, such as shown in Fig. 13; the first needle puncture being made at a the second at b and so on around the triangle. The next to the last needle penetration made at c and the last one at a. The last stitch s" between the points 0 and (z is noticeably longer than the adjacent stitches and the stitch s therefore stands out prominently and may be selected at a glance for raveling out the seam when it is desired to remove the ticket from the article to which it is attached. The feed wheel 15 is adapted to make one revolution for three complete groups of stitches and may therefore be divided into three similar sections each 120 in extent.

The machine is preferably equipped with thread-cutting and thread-end gripping mechanism constructed substantially in accordance with the disclosure of my copending application Serial No. 435.599, filed January 7, i921, and comprising the throat plate 26 having mounted on its under side the thread-end gripping lever 27 in the form of a bellcrank actuated by a link connection 28 from the lower end of an arm 29 fixed to a rock-shaft 3O journaled in a bracket 3 screwed rigidly at 32 to the bracket-arm 4. A two-armed lever 33 is secured to the rockshaft and is actuated by the three similar cam-plates 3e mounted peripherally on the feed-wheel 15. Each of the cam-plates 3-Ll comprises a lateral projection and notch 36 so spaced peri iherally of the feed-wheel 15 as to coactsimultaneously with the opposite ends of the lever 33. That is, when the upper end of the lever 33 rides up on the projection 35, Fig. l, the lower end of such lever enters the notch 36. Also when the lower end of the lever 33 rides out of the notch 36, the upper end rides off of the projection 35. The lever 33 is thus given a single toandfro rocking motion for each stitching period, and the timing is such as to cause the thread-gripper 27 to wipe across the needle-hole 37 after the looper has pulled down the beginning end I; of the needle-thread and substantially as the needle reaches the end of its first rip-stroke, thus seizing the needle-thread end 6 and gripping it against the under surface of the throatplate, as shown in Fig. 4, until the needle reaches the end of its second rip-stroke. The thread-cutting mechanism comprises a bell reason that the abnormal tension exerted on the thread during the second reciprocation of the needle causes the first stitch s laid on top of the paper, Fig. 13, to cut through the same and damage the work. Any work of delicate texture would be damaged in a like manner whereas a button, being hard, will resist this strain on the thread. To overcome this strain on the thread and prevent this tendency to damage the work is one of the particular object-s of the present improvement.

This object is attained by providing suitable connections with the tension-releasing lever previously described, whereby the heavy intermittent tension is relieved or prevented from closing during the second reciprocation of the needle. Such connections may comprise a cam-follower lever 67 fulcrumed on the screw 68 carried by the bracket 52 and having connected to one of its ends the link 69 of adjustable length and including a headed screw 70 passing freely through a hole in the free end of the lever 60 and threaded to the desired extent into the main body portion of the link 69. A lock-nut 71 secures the screw 70 in the clesired position of adjustment. Adjustably mounted on the other end of the lever 67 is the cam-follower 72 having a groove 72, Fig. 8, the walls of which embrace the lever 67. The follower 72 has a slot 78, Fig. 1, in its. side face through which passes a screw 74 for tightening it upon the lever 67. It also has an upward extension 75 in which is threaded an adjusting screw 76, the head of which is circumferentially grooved at 77, Fig. 10, to receive the spaced extensions 78 of the anchor block 7 9 fixed to the lever 67. By turning the screw 7 6 the cam-follower 7 2 may be adjusted lengthwise of the lever 67 to vary the time at which it is acted upon by the actuating cams 85.

The lever 67 is so located that the camfollower 72 is in position to be acted upon by the cam extension 35 of one of the three peripheral cam-plates 34 previously described. It is preferred to so adjust the follower 72 that the plunger 54 of the intermittent tension will be lifted to release the intermittent tension, as the needle enters the work on its second reciprocation, and hold. it open until the needle reaches the end of its second lip-stroke. The thread will thus be substantially free to run from the supply through the constant tension 48' as the looper expands the needle-loop first seized after the thread-end is gripped by the gripper 27. The strain on the thread will be materially relieved and the danger of the thread breaking or cutting into the work obviated. Also, the danger of pulling the free end of the needle-thread out of the gripper 27 will be overcome, and greater certainty of operation secured.

Many machines having a thread-cutter and thread-end gripper provide a pull-off for drawing a supply of slack-thread through the tension preparatory to the sewing operation, so that enough thread will be available on the work side of the tension. to meet the requirements of the stitch-forming instrumentalities during the formation of the first stitch after the thread end is gripped.

Unless the pulloft is carefully adjusted to pull off exactly the correct amount. of thread the result will be unsatisfactory. If too little thread is pulled off the thread will be unduly strained by the demands of the stitch-forming mechanism. If too much thread is pulled off there will be a surplus of thread between the intermittent tension and the work at the beginning of the third reciprocation of the needle and the needleloop shed by the looper will not be fully drawn up as the looper expands the new needle loop. Even if it were possible to closely adjust the pull-off to meet the re quirements of a given thread, at a given time, the results would not be permanent since the elasticity of the thread varies with its quality, and also varies with changes in the humidity of the atmosphere. For these and other reasons it has been found difficult to maintain a correct adjustment of a pulloff under varying sewing conditions. By eliminating the pull-off and permitting the stitch-forming mechanism to pull from the supply under a constant tension the exact amount of thread required for the expansion of the first needle-loop during the second reciprocation of the needle, it follows that the correct amount of thread is always thus provided between the intermittent tension and the work for the first complete loop shed by the looper to be fully drawn up under normal sewing strains. The initial stitches are thus well set up under all conditions apt to be met with in practice and without the necessity of repeatedly making careful adjustments to meet changing conditions.

Having thus set forth the nature of the invention, what I clainrherein is 2-- l. A sewing machine having, in combination, stitch-forming mechanism, a workholder, means for relatively moving them to sew a. group of stitches, a takeup, a tension device above the work-holder, means for holding the beginning end of the needlecl' thread, and means for holding the tension device released during the second reciprocation of the needle to permit the thread to run freely from the supply and prevent abnormal straining of the thread.

2. A. sewing machine having, in combination, stitch-forming mechanism, a workholder, means for relatively moving them to sew a group of stitches, an intermittent tension device normally operating to tenlit) sion and release the thread during each stitch-forming cycle, means for holding the beginning end of the needlethread and automatic means for preventing the closing of the intermittent tension device during the second reciprocation of the needle.

A sewing machine having, in combination, stitch-forming mechanism, a workholder, means for relatively moving them to sew a group of stitches, a constant tension device, an intermittent tension device normally operating to tension and release the thread during each stitcl1-forming cycle, means for holding the beginning end of the needle-thread, and automatic means for preventing the closing of the intermittent tension device during the second reciprocation of the needle, whereby the exact amount of thread required by the stitchforming mechanism during'the second reciprocation of the needle will be pulled from the supply through the constant tension device.

a. A sewing machine having, in combination, stitch-forming mechanism, a workholder, means including a feed-cam and connections for relatively moving the stitchforming mechanism and work-holder to sew a group of stitches, means for nipping the free end of the needle-thread at the beginning of the sewing, an intermittently operated thread-tension on the thread-supply side of the needle, and means on the feedcam and connections for preventing the normal closing of the intermittent thread-tension during the second reciprocation of the needle.

5. In a sewing machine, a thread-tension device, a tension-releasing cam, a tensionreleasing lever connected to said thread tension device and extending substantially tangentially of said cam, and a cam-follower carried by said lever and adjustable lengthwise of the latter.

6. In a sewing machine, a thread-tension device, a tension-releasing cam, a tensionreleasing lever connected to said threadtension device and, extending substantially tangentially of said cam, a cam-follower carried by said lever, and means for adjusting said cam-follower lengthwise of said lever.

7. In a singletl1read sewing machine, in combination, stitch-forming mechanism including a reciprocating needle and a rotary chain-stitch looper, an intermittent threadtension device normally operating to tension and release the thread during each stitch-forming cycle, a nipper for holding the beginning end of the needle-thread during the formation of the initial stitches, a take-up, a work-holder, a feed-wheel and connections for relatively moving the stitchforming mechanism and work-holder to sew a group of stitches, and means for preventing the normal action of said intermittent thread-tension device during the second reciprocation of said needle, whereby thread may be pulled from the supply by the stitchforming instrumentalities during the formation of the stitch next following the nipping of the beginning end of the needle-thread.

8. In a single-thread sewing machine, in combination, stitch-forming mechanism including a reciprocating needle and a rotary chain-stitch looper, an intermittent threadtension device, a nipper for holding the beginning end of the needle-thread during the formation of the initial stitches, a take-up, a work-holder, a feed-wheel and connections for relatively moving the stitch-forn'iing mechanism and work-holder to sew a group of stitches, and a cam; on said feed-wheel and connections for preventing the normal action of said intermittent thread-tension device during the second reciprocation of said needle, whereby thread may be pulled from the supply by the stitch'forming instrumentalities during the formation of the stitch next following the nipping of the beginning end of the needle-thread.

In testimony whereof, I have signed my name to this specification.

ALBERT F. FIFIELD.

CPI 

